The ability to measure changes in the reinforcing effects of ethanol is an important aspect of basic research on alcohol abuse. The proposed studies focus on techniques to quantify the reinforcing effects of ethanol. Rats will be trained to lever-press for deliveries of ethanol solution during daily experimental sessions. In one series of experiments, changes in the reinforcing effects of ethanol will be examined by observing the manner in which certain pretreatments shift the bitonic "inverted-U" shaped dose- response curve that is typically generated when the number of ethanol deliveries obtained per session (or response rate) is plotted as a function of the amount of ethanol available per delivery (usually changed by varying the ethanol concentration). It is hypothesized that pretreatment with agents that (putatively) decrease or increase the reinforcing efficacy of ethanol (e.g., naloxone or morphine injections) will shift the inverted-U shaped dose response function mostly horizontally, while pretreatments that produce satiety (e.g., ethanol injections) will result in a vertical shift. In a second series of experiments, the reinforcing effects of orally-delivered ethanol will be measured under a progressive ratio (PR) schedule in which the ratio value for each successive reinforcer is increased until the subject fails to respond in a designated period of time. The PR procedure has proven to be a sensitive measure of the reinforcing effects of intravenously-delivered drugs in rats. It will be tested for its ability to measure the relative reinforcing effects of different doses of orally-delivered ethanol, and changes in the reinforcing effects of ethanol after pretreatment with ethanol, naloxone, or morphine injections. A third series of experiments will examine choice between two concurrently-available stimuli as a measure of the relative reinforcing effects of those stimuli. Choice between concurrently-available oral ethanol doses will be studied in lever-press ethanol self-administration experiments. Choice between environmental stimuli previously paired with different orally self- administered ethanol doses (i.e., place conditioning) will also be evaluated as a possible measure of the relative reinforcing effects of two different stimuli given at different times. To the extent that the behavioral techniques examined in these proposed experiments help to refine the measurement of the reinforcing effects of ethanol, they may facilitate research in a number of areas.